1. Field of the Invention
This invention relates to a laser deposition (welding) acceptance judgment method for judging acceptance or rejection of a deposition (weld) portion welded by laser deposition (welding) and an apparatus for the method.
2. Description of the Related Art
To reduce the weight and the cost, a resin molding has been used in recent years as a component of automobiles by, for example, forming the component from a resin. To improve productivity, such a resin molding is split molded in advance and the resulting split moldings are mutually welded to give a resin molding.
To bond the resin materials to one another in this case, bonding by using an adhesive has been done but bonding is likely to fail due to influences of heat. Therefore, a method that heats and melts the resin materials by using a laser beam has been employed recently.
Deposition (welding) of the resin materials by the laser beam is carried out by the steps of superposing a resin material having transmissibility to the laser beam and a resin material having absorptivity to the laser beam, irradiating the laser beam from the side of the transmissible resin material, heating and fusing the absorptive resin material by the laser energy, fusing also the transmissible resin material by the heat and integrally bonding the contact surfaces of both transmissible resin material and absorptive resin material.
Judgment of the deposition condition of laser deposition of the resin materials has been conducted by an inspection by eye with workers manually sampling the products, but involves an extended time and a large cost for the quality judgment. Therefore, the following two methods have been employed for judging whether or not a suitable deposition is achieved.
(1) A method that irradiates a laser beam after deposition and detects the existence or absence of a deposition portion between a resin material on the transmission side and a resin material on the absorption side (refer to Japanese Unexamined Patent Publication No. 2004-361229, for example).
(2) A method that detects the temperature of the deposition portion by a temperature sensor during laser deposition or a method that detects a temperature difference of a portion near the deposition portion before and after deposition, and judges acceptance or rejection on the basis of the temperature difference (refer to Japanese Unexamined Patent Publication No. 10-249941, for example).
According to the method (1), however, the laser beam must be irradiated from an oblique direction to the deposition portion. Therefore, detection of the deposition portion of a resin product having ribs is not possible. Furthermore, the inspection cannot be made during laser deposition as a production step but must be conducted after completion of laser deposition, thereby inviting the problem that productivity drops because an additional inspection step is added.
Because the method (2) uses the temperature sensor, the sensor must be calibrated in accordance with the condition of the resin as the radiation factor changes with heating and melting of the resin material. Even when calibration is done, whether or not a gap occurs between the resin materials cannot be detected when such a gap occurs because the surface temperature is the same. To detect a temperature of a portion near the deposition portion, it is extremely difficult for the temperature sensor to correctly follow the orbit of three-dimensional deposition because a robot for laser deposition moves three-dimensionally.